Cam wear plate for switch blades



Jan. 17, 1950 1.. c. CARISSIMI I 2,494,936

CAM WEAR PLATE FOR SWITCH BLADES Filed Aug. 4, 1948 INVENTOR Car simzATTORNEY Patented Jan. 17, 1950 CAM WEAR PLATE FOR SWITCH BLADES Louis0. Carissimi, Fairfleld, Conn., assignor to Remington Band 11:12., NewYork, N. Y., a corporation of Delaware Application August 4, 1948,Serial No. 42,523

This invention relates to improvements in elec- 'tric motors.particularly motors of the make and break contact type used in electricdry shavers. The invention is directed to improving the make and breakcontact structure for electro-magnetic impulse motors by providing meansfor eliminating variations in adjustment between the contacts caused bydiiierences in expansion of the contact arms and the insulating and wearreceiving members carried by the contact arms for engaging the contactoperating cam. This difierence in expansion has resulted in the bucklingor warping of the insulating strips on the contact arms laterally towardthe operating cam asvariations in temperature occur during the operationof the motor causing it to slow down through changing thecontactadjustment.

The invention overcomes the disadvantage of prior constructions byproviding a transversely slotted or recessed insulating strip formed sothat opposite ends of an insulating strip may be riveted to a contactarm with the recessed or slotted portions separating end sectionsriveted to the contact arm from the central or intermediate portion of"the strip. By having the slots extending from one side of the strip to apoint adjacent the opposite margin leaving a narrow connecting portionat the opposite margin between the end and intermediate sections andarranging these connecting portions at opposite ends of the intermediatesection on opposite sides of the strip, a construction is providedwherein differences of expansion will cause the intermediate section ofthe strip to move relative to the end sections within the plane of thestrip so that the intermediate section of the insulating strip will notwarp or bulge away from the contact arm.

In, the drawing Fig. l is a plan view of the make and break contact sideof an electro-magnetic impulse motor illustrating the invention appliedto the contact arms.

Fig. 2 is an enlarged fragmentary cross section taken on line 2-4 ofFig. 1 illustrating the position of the insulating strip constructedaccording to the invention, on the contact arm and relative to theoperating cam.

Fig. 3 shows the insulating and wear receiving strip provided by theinvention in perspective on an enlarged scale.

The present invention is designed for use with motors constructed asdisclosed in U. 8. Patents Nos. 2.368.951, patented February 6, 1945,and 2 415,715, patented February 11, 1947.

The motor has a stator frame I carrying a field winding 2. Frame I is ofsubstantial U-shape, as

ilustrated in said patents and in Fig. 1, and has the free ends of thelegs forming the U-shape frame providing the stator poles. Frame I ispreferably constructed of laminated magnetizable 3 Claims. (CL 200166)metal of a character well-known in the art. The free ends or poles ofstator frame I have a pair of insulating plate members 3 secured to theopposite side faces thereof in spaced. parallel relation by means ofsuitable bolts 4.

A contact structure of conventional form as shown in the aforementionedpatents has a pair of contact arms 5 each carrying a contact point 6 atone end. Each arm 5 has a spring arm extension 1 extending from theother end connected to a supporting bracket 8 suitably secured by rivetsor the like to insulating plate member 3. This contact structure is of aconventional type now well-known in the art and is connected in circuitin series with field winding 2.

Insulating and wear receiving strips or members 9 are mounted on contactarms Ii, one on each arm. along the inner face for engagement by contactoperating cam I0 on the end of the rotor shaft of the motor so that inthe rotation of the rotor and rotor shaft the cam will alternatelyoperate to allow the contact points to engage to close the circuit tothe field winding 2 and then break engagement of contact points I in'theconventional manner to provide electromagnetic impulses forsecuringrotation of the rotor. The rotor shaft is mounted in suitable bearingsin plate members 3 for free rotation. The usual condenser is shuntedacross the contact points as indicated at II.

The invention is directed particularly to the construction of insulatingand wear receiving strips or members 9. It has been found in theconstruction and operation of these motors that a great many differenttypes of insulating materials are not well adapted to use as insulatingand wear receiving strips 9 due to the fact that they wear too rapidlyor have other disadvantages that make them short lived. It has beenfound that a material known as "nylon eliminates many disadvantages ofother materials when used to provide insulating and wear receivingstrips or members 9 in motors of this character. However, this materialhas a suiilciently different coefiicient of expansion from the structureof the contact arms to result in warping of the center portion of eachmember 9 away from the contact arm and toward contact operating cam II],when considering the relation of these parts as shown in Fig. 1. Thuswarping takes place and increases as the temperature of the motorincreases during operation, due to insulating strip 9, expanding to agreater extent than the contact arm. This warping or bulging oftheinsulating and wear receiving member 8 results from rigidly securingopposite ends of the member to the contact arm by rivets It or othersimilar securing means.

The present invention overcomes this disadvantage caused from thedifferences in the coopposite side of the strip from connecting portionIt for the opposite end section It, as clearly shown in the drawing. Theend sections of the strip are formed with apertures I! to receive rivetsor the like It for securing insulating members 9 to the respectivecontact arm 5 in the positions shown in the drawing.

When insulating and wear receiving members 9 are mounted on contact arms5 in accordance with the invention, intermediate sections It will bepositioned to engage contact operating cam I0. One face of intermediatesection it and corresponding faces of end sections it of each member 9will engage the adjacent face of contact arm 5 on which it is mountedwith end sections it rigidly riveted or otherwise secured to contact arm5.

With this construction it will be understood that as the temperature ofthe motor increases including an increase in temperature of contact armsI and members 9. differences of expansion will occur between members 9and contact arms I. With the construction of members 9 as abovedescribed and shown in the drawing, the greater expansion of members 9relative to contact arms 9 will cause the material forming members 9 totwist or warp member 9 within the plane of the member so thatintermediate section I: will twist slightly in edgewise relation withrespect to end sections ll causing connecting portions 19 to bendslightly into curved form while the face of intermediate section lt endsections it and connecting portions l9 adjacent contact arm 9 willremain in engagement with the surface of the contact arm to which it issecured. This will cause the warping of the material of each member I tocause movement of portions of the member within its own plane and in aplane at right angles to the warping previously experienced with the useof a solid insulating strip. With this new insulating and wear receivingstrip construction intermediate section 19 will not move toward contactoperating cam it away from the contact arm and therefore will not aifectthe adjustment of the contact arm and contacts relative to each otherand the cam.

It will be understood that the invention provides an insulating and wearreceiving member for the make and break contact structure of magneticimpulse motors that will provide for the use of insulating materialhaving different coeflicients of expansion from the contact arm withoutinterfering with the adjustment of the contact arms to secure thedesired uniform speed of the motor while at the same time providing forthe use of insulating material that has better wear resisting propertiesin engagement with the contact operating cam.

The invention claimed is:

1. In an electric motor wherein a magnetizable core is formed to providespaced poles, an armature is rotatably mounted in operative relationwith respect to said poles, on a shaft rotatably mounted in bearingmembers supported by said core, said shaft having a cam member on oneend for operating a make and break contact device, and said make andbreak contact device has a contact arm controlling the make and break ofthe contact device through oscillation thereof by said cam member, thecombination of an insulating strip mounted between said contact arm andsaid cam member to provide an insulating and wear receiving member forsaid arm in contact with said cam member. means rigidly attachingopposite ends of said strip to said contact arm, and said insulating andwear receiving member being formed of a strip having slot means be tweensaid opposite ends extending transverely across said strip from one sideand leaving a bendable marginal portion connecting opposite endstogether and bendable in the plane of said strip to compensate fordiflerences of expansion of said contact arm and contact strip tomaintain said contact strip in engaged relation with said contact armthroughout the length thereof during relative expansion therebetween.

2. In a make and break contact type of electric motor having a contactarm forming part of the contact mechanism with a central portionopposite an operating cam for oscillating the contact arm, thecombination of an insulating and bearing strip between said contact armand cam with the central portion of one face engageable with said camand the opposite face bearing against the adjacent side of said contactarm, means rigidly engaging and attaching opposite ends of saidinsulating strip to said contact arm and said insulating strip having anintermediate and end sections spaced apart in coplanar relation, andbendable connecting portions joining said intermediate section to saidend sections at one margin for relative movement of said intermediatesection to said end sections during bend- .ing of said connectingportions in compensating for differences of expansion between saidcontact arm and insulating strip.

3. An insulating and wear receiving member for the make and breakcontact mechanism of magnetic-impulse electric motors, comprising astrip of insulating material formed of an intermediate and end sectionsarranged in end to end spaced relation, and integral bendable connectingportions attaching each end section to one end of said intermediatesection at one side of said section, one connecting portion being at theside opposite the other connecting portion whereby when said endsections are rigidly secured to a contact arm said intermediate sectionis movable in coplanar relation to said end sections on said contact armduring bending of said connecting portions in compensating fordifferences of expansion between said contact arm and strip.

LOUIS CONBTANCE canrssnn.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Aug. 4,1939 Number Number

